As an example of inorganic metal-containing latex polymer particles which have conventionally been used for such purposes as the detection of components of organisms, diagnosis and the like, there can be mentioned particles which are manufactured by emulsion polymerization between an organic layer wherein hydrophobic vinyl aromatic monomer (which may optionally include comonomer) and magnetic particles are dispersed and an emulsifier-containing aqueous solution. In such emulsion polymerization, water-insoluble organic compounds are made to co-exist so that magnetic particles may efficiently be encapsulated in latex particles (e.g., Patent Document 1).
“Magnetic particles (which are synthesized in the method as mentioned in Patent Document 1) have a shape of polymer-coated magnetic body, and, therefore, the magnetic particles have different sizes depending on the particle size of magnetic body as a nucleus. Hence, it is difficult to keep the size of magnetic particles uniform, in particular when the magnetic body has a particle size in a range of 0.1 to 1.0 μm. Besides, synthetic operation is very complicated.” For this reason, there has been provided another method (e.g., Patent Document 2); latex polymer particles which are a polystyrene- or styrene-butadiene copolymer are previously swollen by organic solvent and by heating, and, then, labeling material such as magnetic substance and fluorescent material is added and mixed by stirring, and, thus, said fluorescent material or the like is embedded in the vicinity of surface layer of the latex polymer particles.
The method of Patent Document 1 of emulsion polymerization for encapsulating magnetic particles in latex polymer particles has some defects. Maybe on this account, in most of other methods, swollen polymer particles are brought into contact with an aqueous solution of fluorescent substance or the like (which is to be chelated where necessary) so that the fluorescent substance or the like may thereby be mixed, or incorporated, into the polymer particles, and, in this manner, magnetic body or fluorescent substance is encapsulated or embedded in latex polymer particles (e.g., Patent Documents 3 and 4). Patent Document 3 discloses latex polymer particles which were manufactured from hydrophobic monomer such as styrene, nonionic water-soluble monomer such as acrylamide and anionic monomer such as acrylic acid, for the purpose of improving the stability of latex polymer particles in aqueous solution and of immobilizing physiologically reactive seed on said polymer particles by covalent bonding or absorption. Patent Document 4, on the other hand, uses, as a comonomer for styrene monomer or the like, a macromer which comprises poly(oxyalkylene) segment having, at one terminal, a polymerizable ethylenic group and, at the other terminal, an active ester group, with a view to providing a reactive microsphere which has excellent stability in aqueous medium, and is capable of stably immobilizing thereon functional substances such as protein by chemical bonding, and on which non-specific adsorption of protein or the like hardly occurs.
Documents which are cited above and below are identified as follows.